Can we have index on indexedDb using dart in flutter web?

I have tried implementing Hive for flutter web, but found out that it doesn't provide adding indexes. The underlying indexedDb provided adding index but Hive doesn't provide (at least I couldn't find any example or docs)

I am trying to implement idb_shim, which has official docs for adding index to database.

When I am trying to add a dart object to indexDb using idb_shim it throws an error UnimplementedError: structured clone of other type for some entries. Following is code to add

      IdbFactory idbFactory = getIdbFactory();
      _db = await idbFactory.open(boxName,
        version: 1, onUpgradeNeeded: this.onUpgradeNeeded);
      var txn = _db.transaction(boxName, idbModeReadWrite);
      var store = txn.objectStore(boxName);
      await store.put(value, key);
      await txn.completed;

Similarly, when I am trying to read the object, it is in form of ArrayBuffer not the JSON object. There is no docs indicating clearly on how to store/read dart objects in indexedDb.

      var txn = _db.transaction(boxName, idbModeReadOnly);
      var store = txn.objectStore(boxName);
      final value = await store.getObject(key);
      print(value); // ArrayBuffer

      await txn.completed;
      return value as T; // throws error when converting to actual dart-object

• Do we need to convert dart-objects to Javascript Objects using dart:js package?

• Do we need to store the object in stringified JSON string? In this case index may not work?

I have found solution to both issues:

Do we need to convert dart-objects to Javascript Objects using dart:js package?

Yes, we need to create different objects with following syntax:

import 'package:js/js.dart';

@JS()
@anonymous
abstract class JsItem {
  external bool get prop1;
  external int get prop2;
  external String get prop3;
  external String get bulk_data;

  external factory JsItem({int prop2 = 0, String prop3 = '', String bulk_data = '', bool prop1 = false});
}

While inserting to IndexedDB you can insert the object JsItem().

Do we need to store the object in stringified JSON string? In this case index may not work?

I have overcome of this issue by converting most of data (excluding indexes properties) to JSON string and inserting into bulk_data. Here prop1, prop2, prop3 are indexes.

Reading the data

While reading the data form indexedDB it comes in format of LinkedList map and all properties can be read as map properties. So it would be helpful to create a helper function like below:

  toDartItem(LinkedMap map){
    return DartItem({ prop1: map["prop1"], 
     prop2: map["prop2"], 
     prop3: map["prop3"], 
     bulk_data: map["bulk_data"], // Convert JSOn to different props as required
    )};
  }